When you're in Crane Stance, you can spend a ki point to increase your unarmed damage die by one size until the start of your next turn-- if it was a d4, it becomes a d6; d6 becomes a d8; d8 becomes a d10; and d10 becomes a d12. This is not an action, and you make the choice when you successfully attack a creature (so you don't waste the ki point on a missed attack.)

Stances might need a bit of a rework. For now, I'll leave them as they are until I think of a way to rework them better. XD